CVE-2026-2799Network attack vector

Memory corruption via stale layout fragment lookup

Published Feb 24, 2026 · Updated Feb 24, 2026

Use-after-free in Mozilla Firefox and Thunderbird before 148 allows remote attackers to corrupt memory during DOM text-fragment lookup. FragmentDirective::FindTextFragmentsInDocument() searched text fragments without first flushing layout, allowing stale layout state to remain reachable during the lookup. Exploitation requires user interaction with attacker-controlled content; the freed object's type and the final consequence beyond memory corruption are not public.

CVSS severity8.8
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Mozilla Firefox and Thunderbird before 148 allows remote attackers to corrupt memory during DOM text-fragment lookup. FragmentDirective::FindTextFragmentsInDocument() searched text fragments without first flushing layout, allowing stale layout state to remain reachable during the lookup. Exploitation requires user interaction with attacker-controlled content; the freed object's type and the final consequence beyond memory corruption are not public.

The record

CVE
CVE-2026-2799
Published
Feb 24, 2026
Updated
Feb 24, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-416, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <148

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <148
Mozilla · Thunderbirdversion=unspecified <148

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5Red Hat SADPCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1203Exploitation for Client Execution

Public exploit references

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Technologies

Your stack

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Your stack

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